Lack of sleep or erratic slumber from working late-night shifts or travel may lead to diabetes and obesity, according to a Harvard study that is the first to tie abnormal sleep patterns to disease.

In a trial of 21 men and women observed in a sleep laboratory, those allowed only 5.6 hours of sleep in a 24-hour period over three weeks had a slowdown in their metabolism and a reduction in insulin production. Those changes can lead to weight gain and increased blood sugar, according to research published Wednesday in the journal Science Translational Medicine.

Sleeping, eating and being active at times that are at odds with the body's internal clock, called circadian disruption, may raise the risk of diabetes and obesity as metabolic changes occur, said Orfeu Buxton, the lead study author. More research is needed to understand the results, he said.